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Chapter 109. Disorders of Platelets and Vessel Wall (Part 2)

Thrombocytopenia Thrombocytopenia results from one or more of three processes: (1) decreased bone marrow production; (2) sequestration, usually in an enlarged spleen; and/or (3) increased platelet destruction. Disorders of production may be either inherited or acquired. In evaluating a patient with thrombocytopenia, a key step is to review the peripheral blood smear and to first rule out "pseudothrombocytopenia," particularly in a patient without an apparent cause for the thrombocytopenia. Pseudothrombocytopenia (Fig. 109-1B) is an in vitro artifact resulting from platelet agglutination via antibodies (usually IgG, but also IgM and IgA) when the calcium content is decreased by blood collection in ethylenediamine tetraacetic. | Chapter 109. Disorders of Platelets and Vessel Wall Part 2 Thrombocytopenia Thrombocytopenia results from one or more of three processes 1 decreased bone marrow production 2 sequestration usually in an enlarged spleen and or 3 increased platelet destruction. Disorders of production may be either inherited or acquired. In evaluating a patient with thrombocytopenia a key step is to review the peripheral blood smear and to first rule out pseudothrombocytopenia particularly in a patient without an apparent cause for the thrombocytopenia. Pseudothrombocytopenia Fig. 109-1B is an in vitro artifact resulting from platelet agglutination via antibodies usually IgG but also IgM and IgA when the calcium content is decreased by blood collection in ethylenediamine tetraacetic EDTA the anticoagulant present in tubes purple top often used to collect blood for complete blood counts CBCs . If a low platelet count is obtained in EDTA-anticoagulated blood a blood smear can be evaluated and a platelet count determined in blood collected into sodium citrate blue-top tube or heparin green-top tube or ideally a smear of freshly obtained unanticoagulated blood such as from a finger stick can be examined. Figure .